Carbon has two stable isotopes, C-12 and C-13. Since they both have the same electronic structure they can both make up the same molecules, but presumably they may perform different functions in biochemistry due to different mass.
Q: Have various stable isotopes of the same atom ever been put to use in pharmacology?
Basic internet research only yielded information about unstable, or radioactive isotopes.
As the linked article from Wikipedia notes:
Deutetrabenazine (trade name Austedo) is a vesicular monoamine transporter 2 inhibitor which is used for the treatment of chorea associated with Huntington's disease and tardive dyskinesia.
Chemically, deutetrabenazine is an isotopic isomer of tetrabenazine in which six hydrogen atoms have been replaced by deuterium atoms. The incorporation of deuterium slows the rate of drug metabolism, allowing less frequent dosing.
Whilst what you have in the above is an isotope of hydrogen, the effect this gives is seen in other compounds belonging to the bioisosteres (chemical substituents or groups with similar physical or chemical properties which produce broadly similar biological properties in the same chemical compound), the purpose being to:
enhance the desired biological or physical properties of a compound without making significant changes in chemical structure
The different mass of the deuterium in the case of deutetrabenzine is thought to tweak the chemistry in useful ways:
However, the C–D bond is a bit shorter, and it has reduced electronic polarizability and less hyperconjugative stabilization of adjacent bonds, including developing an anti-bonding orbital as part of the newly formed bond. This can potentially result in weaker van der Waals stabilization, and can produce other changes in properties that are difficult to predict, including changes in the intramolecular volume and the transition state volume
The urea breath test for Helicobacter pylori uses urea labelled with carbon-13 or carbon-14 to detect the presence of the bacteria, which would metabolize it to carbon dioxide and be exhaled.
You should check the Wiki articles:
If we solely focus on carbon-13 based drugs then there is carbon-13 labeled ibrutinib, carbon-13 labeled midazolam/1′-hydroxymidazolam, carbon-13 labelled aspirin.
Lastly, you can reads this papers:
